Recently, in the audio equipment market, there has been a trend that the function of high-quality reproduction is essential, with the wide spread use of digital audio equipment represented by DVD apparatuses.
Further, in the field of communication represented by cellular phones, there have been strong demands for reinforcement of functions size reduction and the function of high-quality reproduction.
On the other hand, in the housing conditions and the environment surrounding automobiles, there has been a demanding requirement for reduction in occupying spaces and energy consumption.
As speakers and speaker devices capable of satisfying those demands, there is a need for development of speakers and speaker devices capable of preferably reproducing deep bass sounds while having small sizes.
Against the background described above, a conventional technique will be described with reference to FIG. 15.
FIG. 15 is a cross-sectional view showing a conventional speaker device.
As illustrated in FIG. 15, speaker device 54 is constituted by cabinet 51, unit 52 mounted to cabinet 51, and pressure adjusting body 53 placed within cabinet 51.
With speaker device 54, it is difficult to reproduce bass sounds preferably due to the influence of the acoustic stiffness exhibited by the cavity of cabinet 51, since cabinet 51 has a small size.
Thus, as one means for overcoming the problem of the limit of reproduction of bass sounds which is determined by the capacity of the cabinet, in order to enable preferable reproduction of bass sounds with small-sized speaker device 54, there is placed within cabinet 51, pressure adjusting body 53, which is typified by activated carbon and the like.
Next, the operations of speaker device 54 will be described.
When electric signals are applied to speaker unit 52, this will change the pressure within cabinet 51, thereby changing the pressure in the cavity within which pressure adjusting body 53 typified by activated carbon and the like is placed.
Along with this pressure change, air molecules are absorbed by pressure adjusting body 53 or released from pressure adjusting body 53, thereby suppressing the pressure fluctuation within cabinet 51.
As described above, in conventional speaker device 54, cabinet 51 operates equivalently to a cabinet having a large capacity. Further, even though the cabinet has a small size, it is possible to reproduce bass sounds as if speaker unit 52 were mounted in a large-sized cabinet.
Further, as background art information relating to the present invention, there has been known Patent Document 1, for example.
However, conventional speaker device 54 requires placement of pressure adjusting body 53 typified by activated carbon and the like within cabinet 51, in order to realize preferable reproduction of bass sounds.
This has caused the problem of great increase in costs including the cost for pressure adjusting body itself 53 typified by activated carbon, the physical distribution cost for pressure adjusting body 53, the production cost for placing and coupling pressure adjusting body 53 inside of cabinet 51 and also including the cost for processing cabinet 51 and pressure adjusting body 53 in a case where there is a need for working upon the inside of cabinet 51.
[Patent Document 1] Unexamined Japanese Patent Publication No. 60-500645